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MRTU

Full Network Model for CRR Allocation

CRR Educational Class #3

CAISO Market Operations

Market Ops - R. Treinen 12/6/2005 to 12/8/2005 2 MRTU

Why is the FNM Important to CRR Allocation?

The FNM is the underlying cornerstone in the allocation of CRRsThe FNM along with the operating constraints and contingencies model the transmission capacity that is being allocatedShift factors are derived directly from the FNMUnderstanding of the FNM is critical for market participants to effectively request CRR


Course Objectives

Upon completion of this course, you will be able to:

Identify the different components of the full network model, both AC and DCUnderstand the differences between the AC and DC network models


Agenda

The Two Types of FNMsComponents That Comprise the FNMsCAISO Network ModelsThe Process of Developing the FNMsThe DC FNM Model for CRR Allocation


Two Types of FNMs

Alternating Current (AC) FNMUsed in the

Day-ahead integrated forward market (IFM)Hour-ahead Scheduling ProcessReal-time energy balancing market

Direct Current (DC) FNMUsed in the CRR allocation process

Important to understand the differences between the AC and DC FNM


AC FNM

The FNM attempts to model all details of the actual power system networkTo be used in software programs that

Ensure the system is operated in a secure manner in the short term

Construction of operating constraints and procedures

Ensure that the system is planned in a reliable manner in the longer term

New transmission facilitiesNew generation interconnections


Agenda



AC Power System FNM Components

Transmission linesResistance

produces transmission losses

InductanceCreated by magnet field due to alternating currentProduces phase difference between voltage and current

CapacitanceCreating by electrical field due to alternating currentProduces phase difference between voltage and current


AC FNM Components

Equivalent circuit of transmission line

Inductance (Reactance)

Shunt Capacitance(Susceptance)

Shunt Capacitance(Susceptance)

AAVResistance

Bus A Bus B

θ∠ BBV θ∠Voltage Magnitude and Angle


AC FNM Components

Transformers (changing the voltage level)Shunt devices (regulating the voltage)

Capacitor banksSynchronous condensersOthers


AC FNM Components

Substations or switchyardsModeled as buses (bus also referred to as node)

Loads (active power (MW) and reactive power (MVar))GeneratorsHigh Voltage Direct Current lines and convertersFlexible AC Transmission Systems (FACTS) devicesOthersPhase Shifting transformers


Agenda



CAISO Network Model

CAISO maintains networks model (or base cases) for control area facilitiesCAISO makes changes/updates to facilities within the CAISO control area in conjunction with the PTOsAlso checks/compares with network models that the CAISO receives from the WECC


CAISO Network Model

CAISO modelAC transmission model60 kV to 500 kV components modeledBus/Branch modelGeneral Electric PSLF formatDoes not provide details of bus sections and the breakers that connect the bus sectionsIncludes the whole WECC transmission system


CAISO Network Model (continued)

StatisticsThe WECC model

~ 14,000 buses~ 18,000 lines

CAISO control area~ 4,000 buses in CAISO control area~ 6,000 lines in CAISO control area


Different Network Models

Network models generally represent the following seasons/time-of-use periodsSeasons

SpringSummer (may also have summer super peak)AutumnWinter

Time-of-use (TOU)On-peak (heavy load conditions)Off-peak (light load conditions)


Difference in Network Models

Differences between the seasonal/TOU network model include

Generation patternsLine switchingActive (MW) Load patternReactive (MVar) Load patternLine ratingsPlanned line and generation outages


Network Models Historically Used at the CAISOOperations Engineering Department Network Models

Analyze the system for a period up to 1 year in the futureAnalyze proposed clearance (outage facilities) conditionsMake sure the day-to-day operating procedures are up to date

Transmission Planning Department Network Models

Analyze the system for a period of 1 year to 10 years out for planning purposesStudies for generation interconnectionStudies for upgraded/new transmission facilitiesRMR studies


Agenda



Process of Developing Full Network Model

The development of the FNM for both IFM and CRR allocation is a multi-step processStart with a CAISO maintained network modelThis model is then transformed into the Common Information Model (CIM) format

All detailed bus information is added for all buses within CAISO control areaAdd in bus section detailsThis model is now a bus/breaker model

Detailed CIM



Integrated Forward MarketFrom detailed CIMDefault breaker statuses appliedTopology process creates an AC bus/branch modelKnown or Scheduled outages are also applied



CRRFrom detailed CIMAnnual CRR allocation/auction model

Assumes all lines in service unless major sustained outagesDo not want to allocate/auction capacity that will not be there

Monthly CRR allocation/auction modelSelected planned/scheduled outages are appliedDo not want to allocate/auction capacity that will not be there

Topology process creates an AC bus/branch modelAC bus/branch is input into CRR systemCRR system converts the AC model to DC model


Agenda



DC FNM Used for CRR Allocation

The DC model is an approximation of the AC modelReferred to as “Direct Current” network modelAnalysis on this network is linear and resembles analysis on a direct current (not alternating current) network

A direct current network is a network with only resistances and constant (not alternating) voltage sourcesThis type of network is linear


DC Network Model Assumptions

Resistance much smaller than reactanceVoltage Magnitudes are always near rated kVReactive load much smaller relative to active loadReactive flow on lines much smaller relative to active flow on lines


DC Network Model

DC model derivation for the CRR allocation/auction

Start with an AC systemSet all resistances to 0.0

There are no losses

Set all voltages to 1.0 per-unitRemove all loads, generators and any shunt devices


Passive DC Network Model

Conversion from AC to DC for CRR allocation

Results in a Passive network modelNo generationNo load

The Sources from the CRRs that are applied act like generation/importsThe Sinks from the CRRs that are applied act like load/exports


Why Use the DC Network Model?AC system of equations are nonlinearDC model does not model losses

No lossesSource injections equal Sink withdrawalsCRRs do not hedge against losses so loss modeling is not needed

DC system of equations are linearA linear system is much easier to work with as compared to nonlinearCan use the properties of superposition

Constraints that are used in the AC system can be modified (e.g., scaled) to be effectively used with a DC model


Why Use the DC Network Model?

Forward market uses AC model so that forward schedules are feasible with respect to real-timeCRRs are a financial instrument

CRRs are not involved in the Forward or real-time marketsAllocating financial rightsFinancial hedge includes only congestion price difference and does not include transmission loss component


Any Questions?

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